This invention relates generally to compositions effective for removing paints from surfaces and, in particular, environmentally friendly, non-chlorinated paint stripper compositions comprising dimethyl sulfoxide and an environmentally acceptable ester.
Paints typically comprise liquid or semisolid mixtures of (a) film-forming components such as a natural or synthetic resins, polymers, or drying oils, (b) a solvent or thinner, and (c) optional pigments and/or other additives. A wide variety of paints which vary widely in their resins, polymers, solvents, pigments, an d additives have been developed and/or specialized for applications involving a wide variety of surface s and intended purposes. The most common purposes are to protect the surface from corrosion, oxidation, or other types of weathering or deterioration; and/or to provide a decorative effect. The paint is typically applied to a surface to form a thin film disposed on the surface. The resulting xe2x80x9cpaint film,xe2x80x9d will hereinafter, for the purposes of this disclosure, be referred to as xe2x80x9cpaintxe2x80x9d.
The paint often undergoes deterioration over time, or becomes otherwise undesirable, so that a need arises to remove the old paint from the surface, without substantially damaging the surface. Various approaches for removing paint and/or graffiti from a surface were discussed in U.S. Pat. No. 5,346,640. Use of chemical compositions suitable for removing paint, i.e. xe2x80x9cpaint strippersxe2x80x9d are well known in the art. For example, U.S. Pat. No. 3,600,322 describes the use of mixtures of methylene chloride and methanol solvents for stripping paint, varnish or lacquers. While methylene chloride and methanol are effective in stripping paint, both solvents are toxic and volatile, and represent significant toxicological and environmental hazards. Paint stripping compositions containing lactams or lactones, particularly N-methyl-2-pyrrolidone or gamma-butyrolactone, in admixture with other active compounds, for example alkylene glycol ethers, are also known in the art. Compare in this respect WO 86/03,766 and WO 88/06,640 and U.S. Pat. Nos. 5,011,121 and 5,015,410.
U.S. Pat. No. 5,346,640 describes compositions for removing paint or graffiti from surfaces, comprising seven ingredients, including N-methylpyrrolidone, propylene carbonate, isocetyl alcohol, and dimethyl sulfoxide (xe2x80x9cDMSOxe2x80x9d). U.S. Pat. No. 5,753,603 describes the use of mixtures of dipolar aprotic solvents which include N-methylpyrrolidone, gamma-butyrolactone, dimethylformamide, and DMSO, in combination with aromatic and aliphatic methyl ethers for paint stripping applications. Swiss Patent No. CH 670,832 describes the use of paint stripping compositions comprising several ingredients, including (a) resin solubilizers selected esters including methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, diethyl carbonate, ethylene carbonate, diethyl tartrate, triethyl citrate, and gamma-butyrolactone, (b) swelling agents comprising ethylene or propylene glycol and certain ether and/or ester derivatives thereof, (c) polar solvents including dimethylformarnide and DMSO.
Unfortunately, most prior art paint strippers have employed volatile organic compounds or solvents and/or other ingredients that have undesirable degrees of toxicity, and/or potential for environmental damage, such as general air or water pollution. All of the above described compositions include at least one component which presents a disadvantage in the area of health and safety of end-users and manufacturing personnel, or to the environment. Methylene chloride is a known animal carcinogen and a suspect human carcinogen, and many similar chlorinated solvents are similarly suspect. N-methyl-2-pyrrolidone is fetotoxic, and dimethyl formamide is a liver toxin. Gamma-butyrolactone is mutagenic and is a reproductive and developmental toxin and has significant adverse effect on the human central nervous system. Moreover, spills of most of the solvents described in the prior art are listed by the Environmental Protection Agency (EPA) under the code of federal regulations (40 CFR) and the provisions of section 313 of Title III of the Superfund Amendments and Reauthorization Act (SARA) as xe2x80x9chazardous wastexe2x80x9d. Spills of these materials endanger the environment and require expensive remediation efforts to correct. Some states, such as California, are enacting even stricter environmental and/or labeling requirements for materials containing potentially hazardous components that are sold to consumers, such as the above-described paint stripping compositions.
In light of the increasingly stringent environmental and safety regulations which have been and will likely continue to be enacted, a serious need exists for paint stripping formulations that are significantly more toxicologically and environmentally acceptable.
The composition according to the present invention is capable of providing the effective stripping of paint from surfaces while employing components that have very low levels of toxicity, a low cost, and are environmentally acceptable.
In one aspect, the invention relates to a paint stripping composition comprising:
a) one or more environmentally acceptable esters, and
b) dimethyl sulfoxide, which is present in an amount not greater than about 70% by volume of the composition.
In another aspect, the invention relates to a method for stripping paint from surfaces, comprising:
a) contacting a painted surface with a paint stripping composition, and
b) separating at least some of the paint contacted with the paint stripping composition from the painted surface; wherein the paint stripping composition comprises:
i) one or more environmentally acceptable esters, and
ii) dimethyl sulfoxide which is present in an amount not greater than about 70% by volume of the composition.
Additional advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.